Objects on a water surface, i.e. marine objects, can coarsely be detected from a position above the water surface using a radio detection and ranging (radar) device.
Radio detection and ranging devices are based on transmitting an electromagnetic wave towards the object, and detecting an electromagnetic wave which has been reflected by the object. The electromagnetic wave can be pulsed and/or modulated. Common modulation schemes comprise e.g. a frequency-modulated continuous wave (FMCW) modulation scheme or a frequency-stepped continuous wave (FSCW) modulation scheme.
The attainable precision and resolution of object detection are mainly influenced by the properties of the applied electromagnetic wave such as the center frequency or the covered frequency bandwidth of the electromagnetic wave. Furthermore, the propagation scenario of the electromagnetic wave, in particular multipath propagation, influences the attainable precision and resolution of object detection.
Common radio detection and ranging devices for the detection of objects on a water surface operate in the X-band extending from 8.0 GHz to 12.0 GHz. The propagation scenario is non-stationary due to the movement of waves at the water surface and poses significant challenges to object detection. Undesired reflections of the electromagnetic wave at the water surface, also known as clutter, further impede the detection of objects.
Therefore, the detection of objects on a water surface using a radio detection and ranging device is limited to the detection of large objects exhibiting a high reflectivity of the electromagnetic wave. The detection of small objects is usually not possible due to the non-stationary propagation scenario and difficulties in distinguishing small objects from undesired reflections of the electromagnetic wave at the water surface.